1. Field of the Invention
Embodiments of the present invention generally relate to storage system management and, more particularly, to a method and apparatus for facilitating control interface failover in a removable media storage device.
2. Description of the Related Art
A plurality of computers can be configured with various software programs and hardware devices. These computers may communicate with one or more data storage devices (e.g., removable media storage devices, such as automated tape libraries) through a computer network. The data storage devices may implement numerous technologies (e.g., Fibre Channel, SCSI and/or the like) to facilitate the transmission and storage of the data. These data storage devices also utilize various software modules that partition various physical resources (e.g., storage slots, data transfer elements (e.g., drives), controllers, medium transfer elements (e.g., a picker, an accessor and/or any other robotic assembly), magnetic tapes, optical disks and/or the like) into a plurality of logical units (e.g., logical devices that are identified by LUNs). For example, a single tape library system may be partitioned into one or more media changer devices which are presented to one or more hosts as proxies for tape library control software (e.g., a SCSI media changer device server).
Furthermore, these software modules perform various storage tasks and also provide an interface, referred to as a control interface, to a certain media changer device, through which storage system commands (e.g., SCSI media changer commands) and corresponding responses are exchanged. The software modules (e.g., device control software) execute one or more commands for operating the media changer device (i.e., media changer commands). These commands instruct one or more robotic mechanisms to move the removable media (e.g., magnetic tapes) in and out of one or more removable media storage drives (e.g., tape drives).
A removable media storage drive forms a logical path, referred to as a control path, to the interface through which a server sends media changer device commands to control one or more logical units, such as a media changer device. The tape drive may also form a data path to one or more magnetic tapes to which the hosts store the data. For example, a storage system consisting of a host (e.g., a desktop computer) that is connected to a removable media storage device having two or more removable media storage drives (e.g., magnetic tape drives) also includes two host bus adapters (e.g., SCSI controllers) that are connected to a first and a second control port, respectively. This storage system forms two physical control paths to the media changer device for redundancy, if one control path from an adaptor to the controller component fails. Maintaining redundant control paths is a host-based failover solution.